Production of uranium peroxide



Patented May 1, 1951 PRODUGTIONIZOFLURANIUM PEROXIDE .PaulrMohnfUl'zbana, 111., assignor ,-t -:,-the EUnited States of Americaas.represented b y th e U itgfl ,States "Atomic Energy CommissionlNoiDraWing.

DPlication-Augusfifl, 1948,

This invention relates to the production of uranium peroxide, andzrnoremarticularly to the recovery of uraniumoas uranium peroxide fromsolutions :an'crmixtures containin mranimn and still more particularlyto-the production, recovcry "and! or separation :of uranium peroxide-possessing adesirable physical properties from solutions and 'niixturescontaining uranium salts.

The process of producing uranium peroxide-by precipitation from aqueoussolutions :has been carried outias a laboratory procedure in the-past.However, prior *workerswho attempted to precipitate the peroxide "from:sulfuric acid solution were unsuccessful-in securing =any precipitation.Previous workers have noted that the presence of othersaltssuchas-saltsof barium, and -='calcium interfered with the precipitation ofuranium -peroxide. However, under the conditions of precipitation usedin my 'process =practically 100 "of uranium content of the solution issecured in the form of an easily handled *and illterableuraniumperoxi'de.

Accordingly this invention hasas'anpbjectthe production of uranium-peroxide possessing =desirableiphysical properties.

A further "object -of"-this*invention is toprovide a method :of*producing, -recoveringiandlor separating uranium as uranium -p'eroxidefrom solutions ormixtures "containinguramum.

A 'stilrfurther object rof this invention is -to provide :a simple andefficient method *for -producing-an easilyhandled-and nlterab1euraniumperoxide precipitate.

"Still further objects 0f thepresent invention will be i apparent fromthe following description taken in connection with the-appended claims.

Broadly the objects of this invention are -accomplished by thesimultaneous addition of "hydrogen peroxide and a water solubleinorganic basesuch as ammonium-or'alkalrmetal' hydroxide to a uraniumsolution containing uranyl -sa-1ts, such *as uranyl sulfate 6 or *uranyl*nitrate, while maintaining the pH of the solution between 2.5 and 4.

preparationof uranium 'peroxide may be carrie'dout undervariousconditions oftemperatureand-concentrationof reagents. Althoughthe temperature --of "the preparation may be varied over quite a rangeit-was"foundthat-th process could be-carried outquantitativelyatroomtemperatures. 'Ihe-hydrogen-peroxidemay be'tised in anyconcentration up to that of a saturated solution.

'-More-specifically-in' accordance--with the present *invention theuranium peroxide possessing the desirable physical properties isprecipitated from an aqueous uranium solution containing hexavalenturanium salts,such-asuranyl-sulfate, while thesolution'is maintained ata relatively constant pH ihetween;-2-.5 and -4. -;Ihese uraniumsolutions may be'eprepared by converting the uranium present insolutions and "mixtures into a-soluble salt or similarly solublecompoundsand then oxidizing the uraniumin solution-to 'hexavalenturanium by simple aerationvor theaddition of a sufficient amount ofa;peroxide,-such ashydrogemor sodium, nitric 3 acid, permanganate, oreachromata Air isvfairly efiectivebutrather slow .in completing the ox dai ne .Q 7 11? m r activeoxidizinaa ents,maysbeius diin jun tion thairrmtheIIinaLcl an-up- .Hydnogen peroxid th s ranmaldvazitagelover itheother oxidizing agents listedli that i is l ss rrosiv than ,nitric.acid, (and that it does .not introduce a ,metallic v iion which mightinterfere with fthe process or @Qontamnate th ,per des hy ro en -,proxi.de i (als vused th t li s quent recipitation per xide.its'ilnplifies' :the ;;handling sand storage problems jinvolved. ThepI-Ldf the -illal ili n solutiojn'isrma ntainedurelatively constant-lamavalue between 225 and J4 by the goOnS aIit .tadditionhas req ired, p asuitable ;basef;suh as ammonimn hydroxid or sodium Ihy thefinal.hydrogen peroxide-various metallicions such as .ferric imay ;,be\removed lb Precipitation and filtration. fsllfiicienlt (hydrogenperoxide .jin anamomi -equalttobetween 105% ivan. i;200;% o the quantity"theoretically required for the .con-

version of hexavalent uranium present to ura-' nium peroxide is thenad'dedwhile the pH of the solution :is maintained .i-at a relatively.:eonstant valueshetweenizzfirand 'etbye h zsimul aneousradditiQIliOfiflsuitable bases ueh-a-asammonium hydroxide. fire-hydrog n enoxideimay beadded t :-that of;-.a saturate isolutiomab u uranium :neroxidpreeipitates alargaz oa e, granular any l n tecipita e which-settles apd maximise asilmand 1 e a ted :f om th v tion--.or :byr-r-otheresepatation methods such a :by

asaanraqueousasoluitoniimany conten atio ou centrifugal separation orravitati ona1r decantation. The precipitate may thenghewvlashed :w-ithwater to remove adherent mother liquor. The uranium peroxideproducedby-the process of this mvention-l-isieesy,t kh ndleands ssuitabliortth manufacture :Q uranium ompounds of h gh pu ty.

The details of: the present invention will become dioxide. Prior ,tothe..iad ition o o h :jsolution h :filtragrams of U308 per 100 ml.ofsolution. The

amount of hydrogen peroxide added and the pH of the solution werevaried. The rate and amount of sodium hydroxide added was also varied inallbut Examples 7, 8 and 9 in which sumcient sodium hydroxide solutionwas added simultaneously with the hydrogen peroxide to maintain arelatively constant'pH between 2.5 and 4.

Table Uranium Precipitated, Per Cent of Total Hydrogen Peroxide, PerCent of Theory Example Final" An analysis, of the table indicates thatthe precipitation of uranium as uranium peroxide was quantitative onlywhen the pH of the solu-' tion was held relatively constant at a pHbetween 2.5 and 3.5 or when an inordinate amount of hydrogen peroxidewas added. In addition the uranium peroxide precipitate obtained in eachof the first six examples was of an extremely finely divided gelatinoustype that was very difficult to filter and had a very low settling rate;while the uraniumperoxide precipitate obtained in each of the last threeExamples 7, 8 and 9, in which the pH was held relatively constant by thesimu1- taneous. addition of a base, was of a large coarse, granularcrystalline type that was very easy to filter and had a rapid settlingrate. The difference inthe methods used to produce these differing typesof uranium peroxide precipitates is clearly brought out in the followingfour examples.

5 Ewami le 1 To about 300 ml. of a uranyl sulfate solution, containinguranium equivalent to 5 grams of U308 per 100ml. of solution, 100 ml. of27 96 H202 was gradually'addedover a period of one hour while the pH ofthe solution was maintained relatively constant between a pH of 3.6 and3.0 by the simultaneous addition of a suitable amount of an aqueoussodium hydroxide solution. The uranium peroxide precipitatedquantitatively as a coarse, granular non-gelatinous precipitate that asettled very rapidly. This precipitate was very easily filtered on aBuchner funnel in approxi mately 5 minutes.

Example 2 As in Example 1, 100 ml. of 27 /2% H202 and sufficient sodiumhydroxide to maintain the pH at 2.0 was gradually added to 300 ml. of auranyl sulfate solution containing uranium equivalent to 4 approximately15 grams of U308. The uranium peroxide precipitated from the solution asa very finely divided precipitate which almost completely passed throughthe filter paper when filtered on a Buchner filter and was extremelydifficult to separate from the mother liquor.

Also as in Example 1, ml. of 27 /292; H202 and a suitable amount ofaqueous sodium hydroxide was added gradually over a period of one hourto 300, ml. of uranyl sulfate solution containing uranium equivalent to5 grams of U308 per 100 ml. of solution. The pH of the solution wasfirst maintained constant between a pH range of 3.0 and 3.6 and thenallowed to drop to a pH of 2.0. At this pH most of the precipitate wentthrough the paper and was of a very finely divided almost colloidal typethat was most difiicult to filter.

Example 4 To 300 ml. of a highly acid (the pH being approximately 0.4)solution of uranyl sulfate containing uranium equivalent to 5 grams U308per 100 ml. of solution, 100 ml. of 27%.; H202 was gradually addedwithout the simultaneous addition of sodium hydroxide. The uraniumperoxide formed remained dissolved in the solution and the solutionremained clear. At this point the pH of the solution was noted to beless than 0.40. Sufiicient aqueous sodium hydroxide was then graduallyadded over a period of two and three quarter hours to raise the pH fromless than 0.4 to a pH of 3.7. Uranium peroxide started precipitatingimmediately upon the slow addition of the aqueous solution of sodiumhydroxide. The uranium peroxide precipitate of this example wasextremely finely divided and of a gelatinous nature which settled veryslowly and was very difficult to separate from the mother solution byfiltration.

As the above examples clearly show the process of producing uraniumperoxide by maintaining a relatively constant pH between 2.5 and 4 bythe simultaneous addition of a suitable base while adding the hydrogenperoxide to the uranyl salt solution as provided by this inventionquantitatively produces a surprisingly highly desirable superior type ofprecipitate which is very purev and easy to handle, settling rapidly andfiltering easily. a I

The uranium peroxide produced by the above preferred process is verypure and can be used to produce uranium compounds of high purity. It

is desirable in the production of pure uranium peroxide by the processofthis invention that suitable apparatus be employed to avoidintroducing further impurities. Thus it is desirable to employequipmentcomposed of material inert to the reagents employed such asglass, rubberor wood.

Having broadly and specifically disclosed the true spirit and scope ofthe disclosed invention.-

I claim:

1. The process of producing uranium peroxide of a highly desirablecharacter from uranyl sulfate solutions which comprises adding hydrogenperoxide to an aqueous uranyl sulfate solution 5 to convert thehexavalent uranyl salt to uranium peroxide and simultaneously addingsodium hydroxide with the hydrogen peroxide to maintain a relativelyconstant pH between 2.5 and 4.

2. A method of recovering uranium from solutions which comprisesconverting the uranium present to uranyl sulfate; and precipitating theuranium as uranium peroxide by the simultaneous addition of hydrogenperoxide and sodium hydroxide while maintaining the pH of the solutionbetween 2.5 and 4; and separating the uranium peroxide from the mothersolution by filtration.

3. A method of producing an easily filterable uranium peroxide whichcomprises adding hydrogen peroxide to an aqueous solution of uranylsulfate maintained at a relatively constant pH between 2.5 and 4.0 bythe simultaneous addition of sodium hydroxide and separating the uraniumperoxide precipitate by filtration.

PAUL MOHR.

REFERENCES CITED The following references are of record in the file ofthis patent:

Friend: Textbook of Inorganic Chemistry, vol. VII, part III, page 311(1926). Published by Charles Grifiin 8: Company, Ltd., London. (Copy inSci. Lib.)

Rosenheim et 2.1.: Chemical Abstracts, vol. 23, page 4634 (1929). (Copyin Sci. Lib.)

Mellor: Comprehensive Treatise on Inorganic and Theoretical Chemistry,vol. 12, page 72 (1932). Published by Longmans, Green and Company,London. (Copy in Div. 59.)

1. THE PROCESS OF PRODUCING URANIUM PEROXIDE OF A HIGHLY DESIRABLECHARACTER FROM URANYL SULFATE SOLUTIONS WHICH COMPRISES ADDING HYDROGENPEROXIDE TO AN AQUEOUS URANYL SULFATE SOLUTION TO CONVERT THE HEXAVALENTURANYL SALT TO URANIUM PEROXIDE AND SIMULTANEOUSLY ADDING SODIUMHYDROXIDE WITH THE HYDROGEN PEROXIDE TO MAINTAIN A RELATIVELY CONSTANTPH BETWEEN 2.5 AND 4.